Measurement of benzene in human breath associated with an environmental exposure.

The concentration of benzene in breath was measured after exposure to environmental benzene. Five volunteers were exposed to environmental tobacco smoke at different exposure levels and for different exposure durations. The breath samples were collected before, during, and postexposure for up to three hours. Benzene in breath was confirmed as a short-term biomarker of environmental benzene exposure at the sub-ppm level. Less than 10% of the inhaled benzene was expired within three hours following two-hour inhalation exposures, with a greater percentage expired following shorter exposures. An average of 64% percent of the inhaled benzene was absorbed through the lung barrier, with the percentage absorbed decreasing with continued exposure. Benzene biological half-lives of 7.6 and 68 minutes were calculated empirically using a two-compartment model based on the exponential benzene decay curve after correcting the breath concentrations for background breath concentrations. The breath concentration calculated at the end of the exposure by extrapolation of the postexposure breath samples demonstrates a discontinuity with the breath concentration collected during exposure, consistent with equilibrium exchange between blood and breath.